Choosing Between Multiple Content Delivery Networks and Load Balancing: Cotendoʼs CDN Balancer

One of the new companies jumping into the Content Delivery Networking (CDN) arena is Cotendo. They are a fairly new CDN Service Provider and are solely focused on the CDN market. Cotendo's strategy is unique: break into the business by capturing some of Akamaiʼs market share in the Dynamic Content area (Dynamic Site Acceleration). Not a bad strategy. If nothing else, you have to give them some kudos for their uniqueness.

Theyʼve also added a wrinkle to that overall strategy by releasing a CDN Load Balancing product. It's very adjustable. The real time conditions for adjustment rules are:

• Weighted allocation • Geographic location (region, country, state) • Geographic distance (proximity to defined geographic target) • Time of day • DNS based rules / policies via XML configuration • Any combination of the above

Letʼs examine some use cases:

Weighted Allocation – a customer can configure X percentage of their traffic to be delivered by CDN 1, Y percentage of their traffic to be delivered by CDN 2, Z percentage of their traffic to be delivered by CDN 3, and so on. This feature allows a customer to better manage their contracts with CDN providers and to take advantage of the ability to adjust commitments.

Geography – a customer can configure traffic delivery to North American users using CDN 1, to European users using CDN 2, to Asia/Pacific Rim users using CDN 3, and so on. Many CDNs have a geographic expertise - for example, CDNetworks, which sells into the North America market, enjoys the #1 market share position in Korea. If a customer wants to take advantage of that #1 position, they could purchase a contract with CDNetworks combined with Cotendo, delivering all of their content to Korea using CDNetworks and all of their traffic around the world using other CDN providers. This might be even more important with continents such as South America, where CDN penetration is very low. In this case, a geographic CDN Load Balancing capability gives customers the ability to, for example, use Akamai for South America (because they have more POPʼs in South America than any other provider), and then use a cheaper CDN in North America.

 

The defined geographies are:

• Regions – North America, South US, West US, NorthEast US, Midwest US, South America, Europe, Northern Europe, Central Europe, Western Europe, APAC, Other;

• Countries – Over 40 countries with the highest Internet use; and • States – All 50 states

A real world example of geographic CDN load balancing via Cotendoʼs CDN Balancer (CDB) is Shopzilla. Shopzilla funnels traffic out of Florida through Cotendo and traffic from another regions through its other delivery network. You can read more about this at Shopzilla buys itself a holiday gift: a second content delivery network.

Geographic Distance – Balancing based on distance is an incredibly powerful capability. For example, a customer can configure to deliver traffic within 100 miles of the origin server via the origin server, and then all other traffic from their CDN If a customer is globally load balanced and has multiple origin servers they can deliver traffic within 100 miles of the first set of servers from those servers, within 100 miles of the second set of servers from those servers, and then from anywhere else using a CDN. Using the IP Address of the End User and an IP Address to geographic location mapping database, the CDN Load Balancer knows where every End User in the world is located.

Time of Day – a customer can configure to deliver their traffic during peak volume periods (between 8 am and 11 pm) via a very well known and top tier CDN, but, when internet traffic patterns show that demand is very low (for example between 2 am and 5 am), deliver traffic via a much cheaper CDN, or even back from their origin server. These time of day rules offers great flexibility for a customer.

DNS Based Rules / Policies Via XML Configuration – Variables can be created and added to the rules, providing what may be the most powerful feature of the Cotendo CDN Balancer (CDB). Perhaps the best way to describe this concept and the power of its capabilities is through a use case.

Assume as users we've set up a Site Failover capability so that if our origin server goes down our site fails over to Whole Site CDN delivery. To configure this weʼll need to set up a Weighted Allocation rule and define two variables: variable1 represents the proportion of Whole Site CDN delivery and variable2 the proportion of Origin Server delivery. Using Cotendoʼs Site Assure product offering we'll monitor the state of the origin server web site (and thus set the value of each variable) via a probe that's based on a performance measurement product such as Gomez or Keynote. We'll define variable1 (the Whole Site CDN delivery variable) so that if Gomez or Keynote detects the origin server site is down, variable1 is set to a value of 100; if the site is up, variable1's value is 0. In order to set the use case rule properly, weʼll define variable2 (the origin server delivery variable) to be the opposite of the variable1: when the web site is down, variable2's value is set to 0 and when the site is up the value is 100.

 

Having created the variables we can now set an allocation rule so that the weight for Whole Site CDN delivery is based on variable1 and the weight for origin server delivery is based on variable2. If the origin server site is down, the Whole Site CDN Delivery weighted allocation will be defined from variable1 as 100%, the Origin Server weighted allocation will be defined from variable2 as 0%, and all traffic will be delivered by the Whole Site CDN Delivery. When the Origin Server site is up, the Whole Site CDN Delivery weighted allocation will be defined from variable1 as 0%, the Origin Server weighted allocation will be defined from variable2 as 100%, and all traffic will be delivered by Origin.

Newly created rules/policies as well as changes propagate through the system in 2 minutes or less. It's incredible that the Cotendo Load Balancer allows a web site administrator to take immediate automated actions at the CDN level based on real-time web site conditions. The use case is just one example, and the possibilities are endless. The flexibility of the rules/policies functionality and what it can now do for web sites at the CDN level is just amazing.

Rules can be in any combination - All of the above rule capabilities can be combined to meet virtually any unique set of requirements. For example, users can combine:

• A Weighted Allocation and Geographic Location rule; • A Geographic Location and Time of Day rule; and • A Weighted Allocation, Geographic Location; and Time of Day rule. The combinations are endless.

Finally, There are some nice things about the way the Cotendo solution functions:

1. the changes take effect immediately; 2. itʼs transparent to the end user; and 3. thereʼs no minimum CDN traffic that needs to go thru Cotendo.

Cotendo's CEO, Ronni Zehavi, says “Cotendoʼs CDN Balancer (CDB) gives a content provider the ability to allocate web traffic or audiences based on monetization strategy or business and IT policies. Rules can be set on the CDB to implement content delivery policies which optimizes objectives such as user experience, system performance and/or cost of delivery.”

In the end, the Cotendo CDN Balancer (CDB) is finally giving users choice and flexibility when it comes to matching their web site delivery business needs and requirements with the available choices in the CDN marketplace. This is amazingly powerful.

We see this as a very positive start for Cotendo, offering product differentiation and also allowing Cotendo to wedge their way into many new accounts through the introduction of their CDN Load Balancer.

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